The present invention relates generally to an expansion anchor, and more particularly to an expansion anchor which is especially suited for suspended ceilings and other suspended elements, such as pipes, ducts and the like.
Many different types of expansion anchors are already known in the art. However, in all of these it is necessary that the element which is to be mounted on a support by means of the expansion anchor, be connected to the screw or bolt that serves to effect the expansion of the expansion anchor. If the anchor is to be secured in a support and a suspended ceiling, a suspended pipe, a suspended duct or a similar suspended element is to be hung from it, these prior-art expansion anchors cannot be utilized since the suspended element, such as the ceiling or the like, will in most instances simply be too far downwardly spaced from the expansion anchor and the support in which the latter is anchored.
The prior art has proposed a special expansion anchor for such applications, which utilizes a conical expander member that is placed into a bore hole formed in the support to which the anchor is to be secured. Thereupon, the expansion anchor sleeve is inserted into the bore hole and forcibly driven into the same, so that its leading end slips over the expander member and thereby becomes expanded. The difficulty with this structure is that once the sleeve has been driven into the bore hole and expanded by the expander member, it is not possible to determine immediately whether the extent of expansion is sufficient in order to afford the requisite anchoring effect. If subsequently it is found out that the anchor is not sufficiently firmly anchored in the bore hole of the support, then it is not possible to take any steps to further improve the anchoring effect, an obvious and very decided disadvantage.